This invention relates generally to the testing and assembly of semiconductor components, such as semiconductor packages, BGA devices and modules. More particularly, this invention relates to a conductive polymer contact system for electrically engaging semiconductor components, and to a test method employing the contact system.
Semiconductor components, such as packages, BGA devices and modules, include terminal contacts in electrical communication with the integrated circuits and electronic devices contained on the components. For example, the terminal contacts on semiconductor packages can be in the form of leads, such as j-leads, gull wing leads, butt joint leads, or integral standoff leads. The terminal contacts on BGA devices and chip scale packages can be in the form of bumps, such as balls in a grid array (BGA). As another example, the terminal contacts on electronic modules, such as memory modules, can be in the form of pads, or alternately pins in a grid array (PGA).
In general, the terminal contacts on the components must be electrically engaged during, and following manufacture of the components. For example, for testing the components, temporary electrical connections are made with the terminal contacts, and test signals are transmitted through the terminal contacts. Test systems for testing semiconductor components include test boards and test circuitry in electrical communication with the test boards. The test boards can include interface boards having contactors configured to make temporary electrical connections with the terminal contacts on the components. Representative contactors include sockets, contact sets, and xe2x80x9cPOGO PINSxe2x80x9d.
In these test systems it is advantageous to make temporary electrical connections with the terminal contacts on the components that are reliable, and have low electrical resistance. This requires that the terminal contacts be scrubbed, or alternately penetrated by the contactors, such that oxide layers and surface contaminants on the terminal contacts do not adversely affect the temporary electrical connections. It is also advantageous for the contactors to accommodate variations in the height and planarity of the terminal contacts. This requires that the contactors have a compliancy or flexibility in making the temporary electrical connections. It is also advantageous for the contactors to be inexpensive to make and to maintain, and inexpensive to replace.
The contact system of the present invention includes contactors configured to make reliable, low resistance, temporary electrical connections with terminal contacts on semiconductor components. The contactors have an increased compliancy for accommodating variations in the size and planarity of the terminal contacts. The contactors are also configured to provide increased durability and wear resistance in a production environment. Further, the contact system can be volume manufactured at a low cost, permitting worn contactors to be easily replaced and discarded.
In accordance with the present invention, a contact system for electrically engaging semiconductor components, and a test method for testing semiconductor components, are provided. In illustrative embodiments, the contact system is configured to electrically engage components having terminal contacts in the form of leads, bumps or pads. In addition, the contact system and the test method are illustrated in the testing of semiconductor packages, BGA devices and modules.
In a first embodiment, the contact system includes an interface board having interface contacts in electrical communication with external circuitry (e.g., test circuitry). The contact system also includes a substrate on the interface board. The substrate is configured to float on the interface board, and is restrained by guide pins, fasteners, or a latching mechanism. The substrate preferably comprises a flexible, electrically insulating organic material, such as a glass filled resin (e.g., FR-4).
The substrate includes a pattern of contactors configured to simultaneously electrically engage the terminal contacts on the component, and the interface contacts on the interface board. The contactors include first contact pads on a first side of the substrate, and second contact pads on an opposing second side of the substrate. The contactors also include conductive vias electrically connecting the first contact pads to the second contact pads. The contact pads preferably comprise a non-oxidizing metal, such as gold or platinum, covered with a conductive polymer layer, such as silver filled epoxy. The first contact pads, and the conductive polymer layers thereon, are configured to electrically engage the terminal contacts on the component. The second contact pads, and the conductive polymer layers thereon, are configured to electrically engage the interface contacts on the interface board. The substrate also includes grooves (e.g., saw cuts) between the contactors, which form flexible segments for the contactors, and provide electrical isolation for the contactors.
With the contact system, the terminal contacts on the component are aligned with, and then placed on the first contact pads. The component is then pressed against the substrate using a suitable mechanism, such as a test handler. The conductive polymer layers on the first contact pads electrically engage the terminal contacts on the component, with the conductive particles therein (e.g., silver particles) penetrating oxide layers on the terminal contacts. Similarly, the conductive polymer layers on the second contact pads electrically engage the interface contacts on the interface board. The resiliency of the conductive polymer layers, along with the flexibility of the substrate and the flexible segments, provide an increased compliancy for the contactors. This increased compliancy allows the contactors to accommodate variations in the dimensions and planarity of the terminal contacts on the component.
In a second embodiment, the contact system again includes an interface board having interface contacts in electrical communication with external circuitry (e.g., test circuitry). The contact system also includes a substrate on the interface board. As with the first embodiment, the substrate is configured to float on the interface board, and is restrained by guide pins, fasteners, or a latching mechanism. In addition, the substrate includes a pattern of contactors configured to simultaneously electrically engage the terminal contacts on the component, and the interface contacts on the interface board.
As with the first embodiment, the contactors include contact pads on a first side of the substrate, second contact pads on an opposing second side of the substrate, and conductive vias electrically connecting the first contact pads to the second contact pads. The first contact pads are configured to electrically engage the terminal contacts on the component. The second contact pads are configured to electrically engage the interface contacts on the interface board. However in the second embodiment, an anisotropic conductive polymer layer on the second side of the substrate provides Z-axis conductive paths between the second contact pads and the interface contacts on the interface board. In addition, the substrate again includes slots (e.g., saw cuts) between the contactors, which form flexible segments on the substrate, and provide electrical isolation for the contactors.
A test method performed with the first embodiment contact system includes the steps of: providing an interface board comprising a plurality of interface contacts in electrical communication with test circuitry; providing a floating substrate on the interface board; providing a plurality of movable test contactors on the substrate comprising first contact pads with conductive polymer layers thereon configured to electrically engage the terminal contacts and second contact pads with conductive polymer layers thereon in electrical communication with the first contact pads and configured to electrically engage the interface contacts; placing the component on the substrate with the terminal contacts in electrical communication with the first contact pads and the interface contacts in electrical communication with the second contact pads; and applying test signals through the test contactors and the terminal contacts to the component.
A test method performed with the second embodiment contact system includes the steps of: providing an interface board comprising a plurality of interface contacts in electrical communication with test circuitry; providing a floating substrate on the interface board; providing a plurality of movable test contactors on the substrate comprising first contact pads configured to electrically engage the terminal contacts and second contact pads in electrical communication with the first contact pads and with an anisotropic conductive polymer layer configured to electrically engage the interface contacts; placing the component on the substrate with the terminal contacts in electrical communication with the first contact pads and the interface contacts in electrical communication with the second contact pads; and applying test signals through the test contactors and the terminal contacts to the component.